#include "bits/stdc++.h"
using namespace std;
ifstream f ("ciclueuler.in");
ofstream g ("ciclueuler.out");
int nr[202],l[202][202],rez[202],nrp;
vector<int> v[202];
void euler (int nod)
{
    int x;
    for (x=0;x<v[nod].size();x++)
    {
         if (l[nod][v[nod][x]]==0)
         {
             l[nod][v[nod][x]]=1;
             l[v[nod][x]][nod]=1;
             euler(v[nod][x]);
         }
    }
    nrp++;
    rez[nrp]=nod;
}
int main ()
{
    int n,x,a,m,b;
    f>>m>>n;
    for (x=1;x<=n;x++)
    {
        f>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    euler(1);
    g<<nrp<<endl;
    for (x=1;x<=nrp;x++)
    {
        g<<rez[x]<<" ";
    }
    f.close ();
    g.close ();
    return 0;
}